New Scientist

Thousands of gas leaks under Boston and San Francisco

06 July 2011 by Phil McKenna
Magazine issue 2820.

IF YOU are reading this in the US, the chances are there is a natural gas leak on your street. The US Energy Information Administration estimates that more than 8 billion cubic metres of gas are lost each year somewhere between the point of production and reaching homes across the nation. Some of this “unaccounted-for gas”, as the EIA has dubbed it, is probably down to faulty meters and accounting errors. But not all.

Thousands of unreported leaks are turning up under Boston and San Francisco, according to Nathan Phillips of Boston University. Together with documents from the Massachusetts Department of Public Utilities, it suggests that some of the gas is leaking into the atmosphere from ageing pipelines beneath urban centres.

The leaked gas represents 1.4 per cent of the nation’s total distribution but the methane it contains could scupper one of the best hopes for clean energy.

When burned, natural gas emits roughly half the carbon dioxide of coal, making it a promising “bridge fuel” until cleaner renewable energy sources come online. Germany is poised to use it as a substitute for the nuclear plants it will shut down by 2022 (see “Germany will use coal and gas to plug nuclear power gap”). But natural gas is made mostly of methane, which has more than 20 times the global warming potential of CO₂ over a 100-year period. So gas that leaks from the system instead of being burned has a significant environmental impact.

Robert Howarth of Cornell University in Ithaca, New York, studies shale gas, which is extracted by injecting a mix of highly pressurised water, chemicals and sand underground to crack open the hydrocarbon-rich rock. The process, known as hydrofracking, is controversial because the chemicals could enter drinking water supplies. Nevertheless, shale deposits under the eastern US and in more than a dozen countries, including China, Brazil and Australia, have raised prospects of a “golden age of gas” where global use could rise by more than 50 per cent by 2035.

Howarth has calculated that 2.2 to 3.8 per cent of shale gas leaks out at the well site and an additional 1.4 to 3.6 per cent leaks during transport, storage and distribution – enough to make shale gas a bigger contributor to global warming than coal (Climatic Change, DOI: 10.1007/s10584-011-0061-5).

The study was pilloried by the natural gas industry, which noted the figures for leaks were based on limited data from pipelines in Texas and Russia. Howarth concedes the point, but he says the problem is the reluctance of companies to share their leak data. “This is a really secretive industry, they don’t like regulators and the public looking too closely at what they do and don’t do,” he says.

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